1. Field of the Invention
The present invention relates to a detector of radiation in two wave bands, as well as to a process for the production of said detector. The invention is particularly applicable to thermal imaging.
2. Discussion of the Background
It is known that thermal imaging permits a representation of objects by their thermal emissions. The energy emitted by an object is dependent on two quantities, namely the emissivity .epsilon.o and the temperature To of the object.
A thermal measurement performed in two wave bands makes it possible, by resolving an equation having two unknowns, to determine To and .epsilon.o. Therefore imaging systems able to read two spectral bands are of great interest in thermal imaging.
Detectors of radiation in two wave bands, also known as two-colour detectors, are known in connection with the production of bispectral cameras. Such a camera, constituted by an AGA THV 780 bispectral analyser operating in the band from 3 to 5.5 .mu.m and in the band from 8 to 12 .mu.m is described in the book entitled "Thermographie infrarouge" by G. Gaussorgues, TEC and Doc, Editions Lavoisier.
In this known analyser, the two analysis channels are spatially separated at the optical means of the analyser, which in fact results from the juxtaposing of the two cameras.
The present invention solves the problem of the positioning, in a tolerance cube and as close to one another as possible, of two photodetection elements or detection pixels, which are respectively sensitive to two separate wavelength ranges.
It is a question of spatially locating these pixels in a tolerance volume perfectly determined in accordance with three axes X,Y and Z perpendicular to one another.
The known microelectronics methods do not make it possible to form "planar" pixels on the same substrate.